Drawing apparatus



Oct. 22, 1963 H. c. WEEKS 3,107,430

' DRAWING APPARATUS i v Find Feb. 2o, 1961 2 sheets-sheet 1 GOP/G4 45 47 e 2 Sheets-Sheet 21 Filed Feb. 20, 1961 United States Patent O 3,107,43@ BRAM/ENG APPARATUS Howard C. Weeks, 610 E. 20th St., New York, NIJ. Filed Feb. 2li, 1961, Ser. No. 90,478 16 Claims. (Cl. 33 77) This invention relates to drawing apparatus and more particularly to such apparatus which is adapted to accurately locate lines of perspective on a drawing surface.

Drawing apparatus of the type to which the present invention is directed is particularly suited `for use in locating the lines of a perspective drawing which converge at selected vanishing points. As will be understood, certain types of perspective drawings customarily have two or more of these vanishing points which are located on the horizon line and may be in proximity rwith the drawing surface or remotely disposed with respect thereto, depending upon the point of observation of the object .to be drawn.

Heretofore, apparatus previously employed .for this purpose have exhibited several disadvantages. For example, diliiculties frequently were `encountered in insuring that each group of perspective lines on the drawing converged at the selected vanishing point, and these difliculties have been of special moment in situations in which the selected point is located remote from the drawing area. Additionally, it often is desirable to quickly and easily vary the location of the vanishing points, and many such previous apparatus have proved deficient in this respect. Furthermore, apparatus of the type heretofore employed in many instances have obstructed the field of vision of the artist or draftsman or have otherwise made it difficult to draw the necessary lines. t 1 `One general object of this invention, therefore, is to provide a new and improved drawing apparatus which is particularly adaptable for locating lines of perspective on a drawing surface.

More specifically, it is an object of this invention to provide such an apparatus which is adapted to accurately locate perspective lines in a manner such that each group of lines converges at -a selected vanishing point.

Another object of this invention is to provide an apparatus of the character indicated in which the location of the various vanishing points may be readily varied in a rapid and straightforward manner.

A yfurther object of this invention is to provide a Adrawing apparatus `which affords the artist or draftsman a relativelymunobstructed `view of the drawing surface and which may be quickly and easily removed therefrom.

Still another object of this invention is to provide a drawing apparatus utilizing comparatively simple rnechanical elements, whichfapparatus is economical to manufacture and thoroughly reliable in operation, U

In one illustrative embodiment of this invention, there is provided an apparatus for locating perspective lines on a drawing surface which includes a pair of intersecting straight edges. These straight edges are maintained in slidable relationship with each other and are interconnected by means including a first elongated member. A second elongated member is affixed to the intersection of the straight edges and extends in a direction which is substantially transverse to that of the first elongated member.

in yaccordance with one feature of the invention, there is provided means for moving the elongated members and the connected straight edges along the drawing surface and for simultaneously moving the second elongated member relative to the first member in a manner such that each of the straight edges is directed toward a predetermined point during this movement. As yan illustration, in one particularly advantageous embodiment, the second strument.

ICC

elongated member frictionaliy engages a rotatable axle mounted on the first elongated member between a pair of wheels which rest on the drawing surface. As the wheels move along the drawing in one direction, the axle urges the second member in the opposite direction relative to the first member to similarly move the intersection of the straight edges. The movement of the straight edges is such that lines located by each straight edge in its various positions at all times converge at a selected point.

'In accordance with another feature of the invention,

in certain good embodiments, the axle between the wheels is of conical configuration, and the position at which the second elongated member frictionally engages this axle is adjustable to thereby vary the rate of relative movement of this second member and hence the location of the points to which the straight edges aredirected. In accordance with a further feature of the invention, in some embodiments, the wheels and their axle, together with the second elongated member in engagement therewith, are slidably movable in either direction along the first elongated member. With this arrangement, the apparatus enables the reproduction of the object to be drawn on the drawing surface in accordance with substantially any angle of View.

The present invention as well as further objects and features thereof will be understood more clearly and fully from the following description of a preferred embodiment thereof, lwhen read in conjunction with the `accompanying drawings in which:

FIGURE l is a top plan view of a drawing yapparatus which is illustrative of a preferred embodiment of the invention;

FIGURE 2 is an enlarged vertical sectional view taken along the line 2 2 in 'FIGURE l; v

' FiGUR-E 3 is yan enlarged Ivertical sectional view taken along the line 3 3 in FIGURE l;

FIGURE 4 is a perspective view of a portion of the apparatus;

FIGURE 5 isa fragmentary sectional view taken along the line 5 5 in FIGURE 1; and

`FIGURES 6i through 10i are schematic illustrations similar to FIGURE l but showing various parts of the apparatus in different relative posi-tions.

Referring initially to FIGURE l of the drawings, there is shown a drawing ,apparat-us which includes 4a pair of elongated, relatively tlat'armsl and 16. These arms advantageously are fabricated from a transparent, plastic material and are each provided with a centrally located, longitudinal slot-17 which extends substantially the entire [length thereof but terminates short of the arm ends. The arms l5 and le respectively include longitudinal edges l and 19 which are straight and serve as guides for -a pencil (not shown) or other drawing in- If desired, the slots 17 likewise may be employed for this purpose, in which case the width of the slots should of course be sufficient to receive the point of the drawing instrument therein.

The elongated arms l5 and lo are positioned one above the other on a substantially horizontal .drawing surface 24 and cross or intersect intermediate their ends. An upstanding pin 20 is disposed at the intersection of the arms l5 and 16, and this pin extends through the slot 17 in each arm to maintain the arms in slidable relationship with each other.k As best shown in FIGURE 3, the lower extremity of the pin Ztl terminates in a dish-shaped sliding contact 2l. The upper lend of the pin is fixedly secured to one end of an elongated connecting bar 22 of rectangular cross-section which is disposed in substantial coplanar relationship with the arms l5 and 16. A coating 23 of rubber or other resilient, slippage-resistant material is provided on the upper longitudinal surface of the bar 22, for purposes that will become more fully apparent hereafter.

One end of a relatively short connecting rod 25 is pivotally and slidably atiixed to the elongated arm in by an upstanding pin 26. The upper end of this pin is rigidly secured to the rod 25, and the pin extends downwardly through the slot I7 in arm I6 and is provided at its lower end with a dish-shaped. sliding contact 27. In a similar manner, one end of a second connecting rod 3@ of equal length is maintained in pivotal, sliding relationship with the elongated arm by an opstanding pin 3i. rIlle pin 31 is rigidly secured to the rod 3i) and extends downwardly therefrom through the slot I7 in arm l5 to a sliding contact 32 at the lower pin end. In the position shown in FIGURE l, the connecting rods and 3@ are each located adjacent one end of their respective arms 16 and 15 and extend horizontally on opposite sides of the elongated bar 22 in a direction parallel thereto.

The connecting rods 25 and 3i) are maintained in rigid but adjustable relationship with each other by an elongated rod 35. Thus, as best shown in FGURES l and 5, the free end of the connecting rod 25 is iixedly secured intermediate the ends of a transversely extending sleeve which is disposed around the rod 35' adjacent the lett end thereof, as viewed in these iigures, and is adjustably secured to the rod by a thumb screw 37. Similarly, the free end of the connecting rod 36 is atlixed intermediate the ends of a sleeve 33 which extends around the rod 35 adjacent its right end and is adjustably secured thereto by a thumb screw 39. The connecting rods 25 and 3i) each meet the rod 35 at a right angle, and together with rod 35, serve to interconnect the arms l5 and Id.

Slidably positioned intermediate the ends of the elongated rod 35 is an adjustment mechanism indicated generally at 4). The mechanism 4t) includes two wheels 41 and 42 (FIGURE 3) which are spaced apart on the rod 35 and are rotatably disposed with respect thereto. These wheels are maintained in fixed relationship with each other by an axle 43 connected therebetween. The axle 43 is rotatably positioned on the rod 35 and advantageously is in the shape of a truncated cone with its base extending to the left, as viewed in FIGURE 3, in engagement with the wheel 41, for purposes that will become more fully apparent hereafter,

The elongated bar 22 extends beneath the rod 35 in a direction substantially perpendicular thereto and to the axle 43. The bar 22 is supported by two parallel sleeves 45 and 46 (FIGURES 2-4) which engage the lower surface of the bar and are transversely oriented with respect thereto. These sleeves urge the resilient coating 23 on bar 22 into frictional engagement with the conical surface of the axle 43. The sleeve 45 extends in a direction parallel to the rod 35 on one side ot the adjustment mechanism 4t) and is rotatably disposed around the bight of a U-shaped member 47, the two legs of which extend diagonally upwardly outside the wheels 4l and 42. These legs are each pivotally connected intermediate the ends thereof to the rod 35 by a bracket 43, and their upper ends are interconnected by a horizontal rod 49. The sleeve 46 is located on the opposite side of the mechanism 40 and is rotatably carried by the bight of a U-shaped member The legs of the member 5'9 likewise extend diagonally in an upward direction outside the wheels 41 and 42 and are each pivotally secured intermediate the ends thereof to the rod 35 by a bracket 51. A rod 52 interconnects the upper ends of these latter legs.

As best shown in FIGURE 4, a bar is positioned above the conical axle 43 and extends between the wheels 41 and 42 in a direction transverse to that of the axle axis and the elongated rod .35. The bar 55 is provided with horizontally extending transverse apertures 56 and 57 adjacent the ends thereof which accommodate the respective rods 49 and 52. Two elongated plates di) and l. are atixed to the bar 55 adjacent the aperture and extend downwardly therefrom on opposite sides of thc elongated bar 22 to form a guideway 62. Similarly, two elongated plates 63 and 64 (FIGURE 3) extend downwardly from the bar 55 adjacent the aperture 56 and form a second guideway 65. A pair of stop members 65 respectively interconnect the lower ends of the plates 63 and 61 and the lower ends of the plates 63 and 64 beneath the bar 22.

A rod 7) is rigidly secured to the bar 55 intermediate the ends thereof, and this rod extends upwardly through an elongated slot 69 in a horizontal plate 72 which forms a part of a housing 73. The housing 73 substantially encloses the adjustment n eehanism 4G and includes depending side panels 76 having oppositely disposed apertures 77 through which the rod 35 slidably extends. A collar 74 is loosely disposed around the rod 70 on the side of the plate "2 adjacent the bar 55. This collar is provided with an upstandng threaded portion 74a of reduced diameter which extends through the elongated slot 69 and accommodates a knob 7i on the opposite side of plate 72. rhe rod 70 protrudes above the collar portion 74a into the knob 71 and is axially movable with respect thereto. rhe portion 74a includes two oppositely dis posed notches 73 and 79 (FIGURE 2) at the lower end thereof which receive the edges of the plate 72 adjacent the slot d. in the tightened position of the knob '71 (the position shown in FlIGURES 2 and 3), the plate 72 is firmly held between the knob and the collar 74 to prevent relative movement between these parts. Upon the loosening or" the knob 7l, the slot G9, which is substantially parallel to the rod 35, permits lateral movement of the collar 74, the rod 70, the bar 55, the plates 69, 61, 63 and 64 and the elongated bar 22 with respect to the housing 73 and the conical axle 43, for purposes that will become iore fully apparent hereafter.

A substantially U-shaped, wire spring 75 is positioned between the bar 55 and the housing plate 72. The bight of spring 75 is suitably secured to the under side of the plate 72, while the spring legs slope downwardly therefrom at an angle which is equal to the angle ot taper of the conical axle 43, as best shown in FIGURE 3. These legs each engage the bar 55 to urge the bar, the rods 49 and 52 andthe upper ends of the arms of U-shaped members 47 and 5t) in a downward direction, viewed in FIGURES 2 4, relative to the housing 73 and the elongated rod 35. The members 47 and Si) thereby tend to pivot about the rod 35, and the sleeves 45 and 46 thereon urge the resilient coating 23 on the bar 22 upwardly into frictional engagement with the conical surface or" the axle 43. The arrangement of the spring 75 is such that, for all positions of the bar 22 relative to the axle 43, the coating 23 is urged into engagement with the `axle surface with substantially equal force.

In use, the drawing apparatus rests on the drawing surface 24 where it is supported by the sliding contacts 2l, 27 and 32 and the wheels 41 and 42. In the position shown in FIGURE 6, the adjustment mecL :mism 40 is located midway between rods 25 and 36, as is the clongated bar 22, and the rod 35 is disposed parallel to a horizon line HL adjacent the upper portion of the drawing surface 24. The pin 2i! at the intersection of the elongate arms 15' and I6 is oriented between the rod 35 and the horizon line. As the adjustment mechanism 4i) is moved along the drawing surface in a given direction perpendicular to the horizon line, the pins 26 and 3l affixed to the rods 25 and 3i) likewise move in this direction at the same rate. The piu Ztl at the intersection of the drawing arms i5 and lo also moves in this direction, but at a rate that is less than the rate of movement of pins 26 and 3l. Thus, as the mechanism 4:3 is moved toward the horizon line from the position shown by full lines in FIGURE 6 to its dotted line position, for cxnmple, the wheels 4i and 42 (FIGURE 4) rotate about the elongated rod 35 to similarly rotate the conical axle 43. As the axle revolves, the bar 22 in frictional engagement with its conical surface moves longitudinally, relative to the rod 35 and the pins 26 iand 3l, in a direction opposite to the direction of movement of the adjustment mechanism 4t). As a result, the pin 2t? on bar 22 is drawn toward the adjustment mechanism and moves toward the horizon line at a rate less than that of the pins and 31. In a similar manner, as the adjustment mechanism liti, and hence the pins 26 and 3l, are moved from their dotted line position toward their full line position, the conical axle d3 urges the bar Z2 and the attached pin 20 away from the adjustment mechanism so that the rate of movement of pin 20 toward its full line position is less than that of the pins Z6 and 31.

The triangulation resulting from the different rates of movement of the pin 2d on the one hand and the pins 26 and 31 Aon the other determines the various positions of the straight edges IS and I9 and insures that lines of perspective drawn on the drawing surface 24- along these straight edges converge at selected vanishing points on the horizon line. As an illustration, in FIGURE 6, perspective lines drawn along the straight edge i8,

l if extended, will converge at a vanishing point Vil on the line HLLwhile perspective lines nos drawn along the straight edge 19 will converge at a vanishingpoint VP2 on line HL The arrangement is zsuch that the str "aight edges .1S `and i9 at all times are directed toward the selected vanishing points as the adjustment box d is moved along the drawing surface.

The spacing between the vanishing points WPI aid VPZ on the horizon line is readily adjustable in accordance with the point of observation of the object to be drawn. To accomplish lthis adjustment, the knob 7i is unscrewed to permit lateral movement of the upstanding -rod 70 relative to the slot 69 in the housing plate 42, The knob 71 is then moved relative to the slot 69 to control the position of the elongated bar 22 on the conical surface of the axle 53. For example, in cases in which the selected vanishing points are relatively close together, as shownrby the points VPl and VP2 in FIGURE, 6, the knob 7l is moved to the left from the position shown in FIGURE l to its FIGURE 6 position. The attached bar 55 (FIGURE 4) and the plates forming the guideways 62 and 65 similarly move i-n this direction relative to the rods 49 and 52 to thereby position the bar Z2 beneath the end of the axle 43 having the greater diameter. The knob 7i is then tightened to hold the various parts in their new positions. As the thus adjusted mechanism it@ is moved along the drawing surface Sti, the bar 2.2 moves relative to the mechanism da at a rate more rapid than when the knob 7l is in its FIGURE l position,V

with the result that the vanishing points are closer together. Y

In a similar manner, in situations in which the selected vanishing pointsare spaced farther apart along the horizon line, the knob 7l is moved relative to the slot 69 in `the opposite direction to the position shown-in FIGURE 7, for example, to move the elongated bar 273 to a position in engagement with a portion of the conical axle t3 having a smaller` diameter. As the adjustment mechanism 4t? is moved along the drawing surface with the knob 7l in this new position, the rate of movement of the bar 22 relative kto mechanism du is decreased, with the result that perspective lines drawn along the straight edges I8 and I9, if extended, converge at vanishing points which are spaced farther apart along the horizon line. knob 7l in either direction along the slot 69, the spacing between the vanishing points is quickly and easily adjusted to provide the desired degree of separation therebetween.

As indicated heretofore, the adjustment mechanism 46 is slidably mounted on the elongated rod 35. As a result, the location of one or more of the vanishing points on the horizon line rnay be varied to permit a variety of angles of View to be drawn of the object. For example, as the ladjustment mechanism l0 is moved to the right along the rod 35 from the position show-n in FlGURF. l `to the position shown in FIGURE 8, the bar 22 and the pin 20 at the intersection of the arms I5 and 15 likewise move in this direction. The arm i6 thereby pivots in a clockwise -direction about the pin 26 and is directed toward a vanishing .point (not'shown) which is remotely spaced from the drawing surface Z4, while the arm l5 pivots in a clockwise direction about the pin 31 and is directed toward a vanishing point VP located on the surface 24 slightly to the left of the center of the horizon line. Conversely, by sliding the adjustment mechanism 4t) along the rod 35 to the lleft, the vanishing point for perspective lines drawn along the arm I5 moves progressively farther away from the center of the horizon line, while that result-ing from perspective lines drawn along the arm I6 approaches this center.

FIGURE 9 is illustrative of the manner in which the apparatus may be adjusted in accordance with a particular angle of view of the object to be drawn. As will be understood, a horizontal line P on the drawing surface represents the line of intersection between this surface and the picture plane, and a rectangle 90 having one corner located on the line P represents a plan view of the object. The rectangle 9d is disposed above the line P, as viewed in FIGURE 9, and the angles at which the sides of the ectangle intersect"lineP correspond to the artists viewpoint of the object. To adjust the'apparatus, it is positioned on the same side of the picture plane line P as the rectangle 9i) with the elongated rod 35 extending in a direction parallel to line P. The intersection of the straight edges I3 and I9 is on the picture plane line, and the adjustment mechanism it? is moved along the rod 35 until the intersection is superimposed over the corner of the rectangle located on this line. A perspective View of the object corresponding to the rectangle 90 is then drawn with the thus adjusted mechanism 4t? located on the rod 35 in a position corresponding to the desired angle at which the object is viewed.

To accurately locate the lines on the drawing surface which represent vertical lines on the object being drawn,

` a rectangle 94 (FIGURE 10) is drawn on the drawing The arrangement is such that, by'movement of the K surface in a manner similar to the rectangle 9i) of FIG- URE 9, with one corner located on the picture plane line P, and a vertical dotted line is drawndownwardly from this corner. The apparatus is placed on the drawing surface with the elongated rod 35 extending in a direction perpendicular to the picture plane line and with the bar 22 superimposed over this line. The straight edges It@ and 19 are oriented along the line 95, and the mechanism dit is then moved to selected locations along the picture plane line to position the straight edge 18 in alignment with each of the remaining three corners of the rectangle 94. Dotted lines 95a-, 95h and 95C, respectively drawn along the straight edges in these three positions, pass through the picture plane and converge at a point 96 on the vertical line 95, representative of the point from which the object is viewed. i

In many types of perspective drawings, lines 97, which represent the vertical lines of the object being drawn, are vertically disposed on the drawing surface. The lines 97 are quickly and easily located on the drawing by placing them along the vertical line 95 and along dotted vertical lines 98a, 9S!) and 9de, respectively drawn through the points at which the converging lines 95a, 95b and 95e intersect the picture plane line P. For perspective drawings in which the lines representative of the vertical lines of the object are converging, they illustratively may be drawn directly along the lines 95, 95a, 95b and 95C. j In certain particularly advantageous embodiments of the invention, the ratio between the minimum diameter of the conical wie 43 (FIGURE 4) and the diameter of the wheels all and 4?. preferably is within the range of from about .O6 to .25,'while the ratio between the maximum diameter of the axle 43 and that of the wheels is within the range of from about .50 to 1.00. As a result, the various lines of perspective are located with an extremely high degree of accuracy while affording a wide variation in the spacing between the vanishing points on the horizon line. in other good embodiments, however, these ratios may be outside the above ranges without departing from the spirit and scope of the invention.

As indicated heretofore, in the illustrated embodiment of the invention, the elongated arms l and i6 advantageously are fabricated from a transparent material, wit the result that the artist or drattsman is afforded a substantially unobstructed View of the drawing surface ft). For some applications, however, particularly in cases in which the number of perspective lines to be drawn is relatively small, these arms may be constructed of other appropriate materials without deleterious effect.

The erms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described, or portions thereof, it being recognized that various modifications are possible within the scope ot the invention claimed.

I claim:

In an apparatus for locating perspective lines on a drawing surface, in combination, a pair of intersecting straight edges supported on said drawing surface, means mounted at the intersection of said straight edges for maintaining the same in predetermined movable relationship with each other, means including a irst elongated member connected between said straight edges and angularly movable with respect thereto, a second elongated member aliixed to said first-mentioned means and extending toward said first elongated member, and means for moving said rst elongated member and the connected straight edges along said drawing surface and for simultaneously moving said second elongated member relative to said tirst elongated member, to similarly move the intersection of said straight edges, each of said straight edges being directed toward a predetermined point during its movement.

2. An apparatus for locating perspective lines on a drawing surface comprising, in combination, a pair of intersecting straight edges supported on said drawing surface, connecting means mounted at the intersection of said straight edges for maintaining the saine in pivotal, sliding relationship with each other, means including a first elongated member pivotally connected to each said straight edge at a point spaced from said intersection, a second elongated member atilxed to said connecting means and extending toward said first elongated member, and means for moving said rst elongated member and the points at which it is connected to said straight edges along said drawing surface and for simultaneously moving said second elongated member relative to said tirst elongated member, to similarly move the intersection of said straight edges, cach of said straight edges being directed toward a predetermined point during its movement.

3. ln an apparatus for locating perspective lines on a drawing surface, in combination, a pair of intersecting straight edges supported on said drawing surface, connecting means mounted at the intersection of said straight edges for maintaining the same in sliding relationship with each other, means including a first elongated member connected between said straight edges and angularly movable with respect thereto, a second elongated member aiiixed to said connecting means and extending toward said first elongated member, and means for moving said rst elongated member and the connected straight edges along said drawing surface and for simultaneously moving said second elongated member relative to said first elongated member, to similarly move the intersection of said straight edges, each of said straight edges being directed toward a predetermined point during its movement, said last-mentioned means including means for varying the rate of relative movement between said elongated members, to thereby vary the location of the points to which said straight edges are directed.

4. An apparatus for locating perspective lines on a drawing surface comprising, in combination, a pair of intersecting straight edges supported on said drawing surface, connecting means mounted at the intersection of said straight edges for maintaining the same in pivotal sliding relationship with each other, means including a first elongated member pivotally connected to each of said straight edges and extending therebetween, a second elongated member afxed to said connecting means and extending in a direction substantially transverse to that of said first elongated member, and means for moving said first elongated member and the connected straight edges along said drawing surface, said second elongated member, and hence the intersection of said straight edges, moving relative to said rst elongated member during the movement thereof, said last-mentioned means including means for varying the rate of said relative movement.

5. An apparatus for locating perspective lines on a drawing surface comprising, in combination, a pair of intersecting straight edges supported on said drawing surface, connecting means mounted at the intersection of said straight edges for maintaining the same in pivotal sliding relationship with each other, a first elongated member extending between said straight edges, pivot means spaced from said intersection for pivotally connecting each said straight edge to said first elongated member, a second elongated member affixed to said connecting means and extending toward said first elongated member, and operating means for moving said first elongated member and the pivot means for each ot said straight edges along said drawing surface, said second elongated member, and hence the intersection of said straight edges, moving relative to said first elongated member during the movement thereof, each of said straight edges being directed toward a predetermined point during its movement, said operating means including means for varying the rate of relative movement between said elongated members.

6. An apparatus for locating perspective lines on a drawing surface comprising, in combination, a pair of intersecting straight edges supported on said drawing surface, connecting means mounted at the intersection of said straight edges for maintaining the same in pivotal, sliding relationship with each other, a rst elongated member extending between said straight edges, pivot means spaced from said intersection for pivotally connecting each said straight edge to said first elongated member, a second elongated member affixed to said connecting means and extending in a direction transverse to that of said tirst elongated member, said straight edges and said elongated members being substantially oriented in a single, flat plane, means for moving said first elongated member and the pivot means for each of said straight edges along said drawing surface and for simultaneously moving said second elongated member relative to said first elongated member, to similarly move the intersection of said straight edges, each of said straight edges being directed toward a predetermined point during its movement between said elongated members.

7. ln an apparatus for locating perspective lines on a drawing surface, in combination, a pair of intersecting straight edges supported on said drawing surface, means mounted at the intersection of said straight edges for maintaining the same in predetermined movable relationship with each other, means including a first elongated member connected between said straight edges and angularly movable with respect thereto, a second elongated member afiixed to said first-mentioned means and extending toward said tirst elongated member, a pair of wheels rotatably mounted on said first elongated member and movable along said drawing surface, an axle interconnecting said wheels, and means for urging said second elongated member into frictional engagement with said 9 axle, movement of said wheels, said first elongated member and the connected straight edges along said drawing surface in one direction rotating said axle to longitudinally move said second elongated member relative to said first member in the opposite direction, to similarly move the intersection of said straight edges, each of said straight edges being directed toward a predetermined point during the movement of said wheels.

8. An apparatus for locating perspective lines on a drawing surface comprising, in combination, a pair of intersecting straight edges supported on said drawing surface, connecting means mounted at the intersection of said straight edges for maintaining the same in pivotal, sliding relationship with each other, a first elongated member extending between said straight edges, pivot means spaced from said intersection for pivotally attaching each straight edge to said first elongated member, a second elongated member affixed to said connecting means and extending toward said first elongated member in a direction transverse to that of said first member, said straight edges and said elongated members being substantially oriented in a single, flat plane, a pair of wheels rotatably mounted on said first elongated member and movable along said drawing surface, an `axle interconnecting said wheels, and means for urging said second elongated member into frictional engagement with said axle, movement of said wheels, said rst member, and the pivot means foreach of said straight edges along said drawing surface in one direction rotating said axle to longitudinally move said second elongated member relative to said first member in the opposite direction, to similarly move the intersection of said straight edges, each of said straight edges being directed toward a predetermined point during said movement.

9. An apparatus of the character set forth in claim 8, in which lthe pivot means for each said straight edge includes means `for varying the position at which said first elongated me-mber is pivotally attached thereto.

10. An :apparatus for locating perspective lines on a drawing surface comprising, in combination, `a pair of intersecting straight edges supported on said drawing surface, connecting means mounted at the intersection of said stnaight edges for maintaining the same in pivotal sliding relationshipwith each other, means including a first elongated member pivotally connected between said straight edges, a second elongated member affixed to said connecting means and extending toward said first elongated member, a pair of wheels rotatably mounted on said first elongated member and movable along said drawing surface, a co-nical axle interconnecting said wheels, means for urging said second elongated mem-ber into frietional engagement with the conical surface of said axle, movement of said wheels, said first elongated member :and the connected straight edges along said drawing surface in one direction rotating said axle to longitudinally move said second elongated member relative to said first member in the opposite direction, to similarly move the intersection of said straight edges, each of said straight edges being directed toward a predetermined point during said movement, and means for moving said second elongated rnember along said conical surface, to thereby vary the rate of said relative movement `and hence the location of the pointsto which said straight edges are directed.

1l. An :apparatus for locating perspective lines on a drawing surface comprising, in combination, a pair of intersecting straight edges supported on said drawing surface, connecting means mounted at the intersection of said straight edges for maintaining the same in pivotal, sliding relationship with each other, means including a rst elongated member connected between said straight edges and angularly movable with respect thereto, a second elo-ngated member afiixe-d to said connecting means and extending in a direction substantially transverse to that of said first elongated member, said straight edges and said elongated members being substantially oriented in a single,

fiat plane, a pair of wheels rotatably mounted on said rst elongated member and movable along said drawing surface, a conical axle interconnecting said wheels, means for urging said second elongated member into frictional engagement with the conical surface of said axle, movement of said Wheels, said first elongated member and the connected straight edges along said drawing surface in one direction rotating said laxle to longitudinally move said second elongated member relative to said lfirst member in the opposite direction, to similarly move the intersection of said straight edges, each of said straight edges being directed toward a predetermined point during said movement, and means for moving said second elongated member in a direction transverse to its longitudinal direction to vary the position of said second member on said conical surface, to thereby va-ryrthe rate of said relative movement and hence rthelocation of the points to which said straight edges are directed.

l2. An apparatus for locating perspective lines on a drawing surface comprising, in combination, a pair of intersecting straight edges supported on said drawing surface, connecting means mounted Yat the intersection of said Astraight edges for maintaining the same in pivotal, sliding relationship with each other, means including a first elongated member connected between said straight edges and angularly movable with respect thereto, a second elongated member aiiixed to said connecting means and extending in la ydirection substantiallytransversel to that of said first elongated member, a pair'of wheels of equal diameter rotatably mounted on said first elongated member Iand movable along `said drawing surface, a conical axle interconnecting said wheels, the ratio between the minimum diameter of said `axle and the diameter of said wheels being within the ran-ge of from about .O6 to .25 and the ratio between the maximum diameter of said axle and the diameter of said wheels being within the range of from about .50* to 1.00, means for urging said second elongated member into frictional engagement wit-lr the conical surface of said axle, movement of said wheels, said first elongated member and the connected straight edges along Said drawing surface in one direction rotating said axle to longitudinally move said second elongated member relative to said first member in the opposite direction,to similarly move the intersection of said straight edges, each of said straight edges being directed toward a predetermined point during said movement, and means for moving said second elongated member in a 'direction transverse 'to its longitudinal :direction lto vary the position of said second member on said conical surface, to thereby vary the rate' of said relative movement and hence 4the location of the points to which said` straight edges are directed. y

13. An apparatus for locating perspective lli-nes on a drawing surface comp-rising, in combination, a pair of intersecting straight edges supported on said drawing surface, `connecting lmeans mounted at the intersection of said straight edges for maintaining the same in pivotal sliding relationship with each other, Ea first elongated member extending between said straight edges, pivot means mounted on each of said straight edges at a location remote from said intersection for kpivotal-ly attachingeach said straight edge to said first elongated member, a second elongated member affixed to said connecting means and extending toward said first elongated member in a direction substantially [transverse to that of said first member, a pair of wheels rotatably mounted on said first elongated member `and movable :along said ldrawing surface, a conical axle interconnecting said wheels, means for urging said second elongated member into 4frictional engagement with the conical surface of said axle, movement of said wheelspsaid first member land the pivot means y =for each lof said straight edges along said drawing surface :in one direction rotating said -axle to longitudinally rnove said second elongated member relative to said first member in the opposite direction, to similarly move the intersection of said straight edges, each of said straight edges being directed toward a predetermined point during the movement of said wheels, and means for moving said second elongated member in a direction transverse to its longitudinal direction to vary the position of sai second member on said conical surface, to thereby vary the rate of said relative movement and hence the location of the points to which said straight edges are directed.

14. An apparatus for locating perspective lines on a drawing surface comprising, in combination, a pair of intersecting straight edges supported on said drawing surface, connecting means mounted at the intersection of said straight edges for maintaining the same in pivotal, sliding relationship with each other, a first elongated member extending between said straight edges, pivot means mounted on each of said straight edges at a location remote from said intersection for pivotally attaching each said straight edges to said first elongated niember, a second elongated member affixed to said connecting means and extending toward said first elongated member in a direction substantially transverse to that `of said first member, said straight edges and said clongated members being substantially oriented in a single, at plane, a pair of Wheels rotatably mounted on said first elongated member and `movable along said drawing surface, a conical axle interconnecting said wheels, spring means for urging said second elongated member into frictional engagement with the conical surface of said axle, movement of said wheels, said rst member and the .tls pivot means for each of said straight edges along said drawing surface in one direction rotating said axle to longitudinally move said second elongated mem-ber relative to said iirst mem er in the opposite direction, to similarly move the intersection of said straight edges, each .of said straight edges being directed tov/ard a predetermined point during said movement, and control means operatively associated `with said spring means for moving said second elongated member in a direction transverse to its longitudinal direction to vary the position of said second member on said conical surface, to thereby vary the rate of said relative movement and hence the location of the points to which said straight edges are directed.

l5. An apparatus of the character set forth in claim 14, which includes means for maintaining the pivot means for each said straight edge in rigid but adjustable relationship with said first elongated member.

16. An apparatus of the character set forth in claim 14, in `which said wheels, said axle, said spring means and said control means are all slidably movable as a unit along said lirst elongated member'.

References Cited in the tile of this patent UNITED STATES PATENTS 2,419,725 Nosser Apr. 29, 1947 FOREIGN PATENTS 726,473 Great Britain Mar. 16, 1955 

4. AN APPARTUS FOR LOCATING PRESPECTIVE LINES ON A DRAWING SURFACE COMPRISING, IN COMBINATION, A PAIR OF INTERSECTING STRAIGHT EDGES SUPPORTED ON SAID DRAWING SURFACE, CONNECTING MEANS MOUNTED AT THE INTERSECTION OF SAID STRAIGHT EDGES FOR MAINTAINING THE SAME IN PIVOTAL SLIDING RELATIONSHIP WITH EACH OTHER, MEANS INCLUDING A FIRST ELONGATED MEMBER PIVOTALLY CONNECTED TO EACH OF SAID STRAIGHT EDGES AND EXTENDING THEREBETWEEN, A SECOND ELONGATED MEMBER AFFIXED TO SAID CONNECTING MEANS AND EXTENDING IN A DIRECTION SUBSTANTIALLY TRANSVERESE TO THAT OF SAID FIRST ELONGATED MEMBER, AND MEANS FOR MOVING SAID FIRST ELONGATED MEMBER AND THE CONNECTED STRAIGHT EDGES ALONG SAID DRAWING SURFACE, SAID SECOND ELONGATED MEMBER, AND HENCE THE INTERSECTION OF SAID STRAIGHT EDGES, MOVING RELATIVE TO SAID FIRST ELONGATED MEMBER DURING THE MOVEMENT THEREOF, SAID LAST-MENTIONED MEANS INCLUDING MEANS FOR VARYING THE RATE OF SAID RELATIVE MOVEMENT. 